Customising error messages is often overlooked, but it’s easy to tailor this experience for your website. See: https://salsadigital.com.au/somepage as an example.
In this exercise you’ll create a custom error message/page. The page could be a graphic, or a useful message.
Create basic Standard pages with an appropriate message for each situation (e.g. http://example.com/notfound and http://example.com/accessdenied)
Go to Configuration → System → Basic site settings.
Type in the paths in the bottom section on Error pages.
Save configuration.